A research project relating to quantum cryptographic communication called secure communication based on quantum cryptography (SECOQC) is known. In SECOQC, have been proposed techniques such as functions generated through distribution of quantum cryptographic keys and used for key exchange based on random numbers distributed and stored in a plurality of nodes, and a protocol named Q3P (quantum point to point protocol).
With the techniques of related art, however, in a case where a node is added or in a case where random numbers are excessively consumed in a node and the node can no longer be used, such node has to be resumed manually. Specifically, in such cases, a key for initial authentication, for example, needs to be set manually by an administrator.